Abstract

Two root-lesion nematode species (Pratylenchus thornei and P. neglectus) reduce the value of Australian wheat production by AUD$123 million per year. Five synthetic hexaploid wheats (SHW) with resistance to both P. thornei and P. neglectus have been identified. To further investigate inheritance of resistance to P. thornei and P. neglectus, doubled haploid (DH) populations between these SHW and the susceptible Australian bread wheat cultivar Janz (90-120 individuals) were tested as 6 replicates in separate glasshouse experiments for each DH population and nematode species. Plants were grown singly in pots of 330 g of pasteurised vertosol containing 3,300 nematodes at constant soil temperature (22oC) and water tension (-2 cm). Analysis of variance (ANOVA) was conducted on nematode populations at 16 weeks of plant growth for each experiment with data transformed by ln(Pratylenchus sp./kg soil + c). Genetic variance (σ2g), heritability (h2) on a line mean basis and minimum number of effective resistance genes were calculated from the ANOVA. Heritabilities for the five DH populations ranged 0.88–0.92 for P. thornei and 0.59–0.88 for P. neglectus populations. The minimum number of resistance genes segregating in the populations was 4, 6, 3, 4 and 4 for P. thornei and 3, 4, 6, 4 and 4 for P. neglectus for the respective five SH parents (Yallaroi/AUS24152), (TAMD870167/AUS18913), CPI13842, CPI133859 and CPI133872. There was no correlation between P. thornei population density and P. neglectus for four of the DH populations and a low correlation for one (TAMD870167/AUS18913 x Janz DHs, r = 0.28, P < 0.01, n = 106). A small number of individual DHs with moderate resistance to both P. thornei and P. neglectus could be recovered from all populations, which will be valuable in pre-breeding for dual resistance. These results indicate that the genes conditioning resistance are mainly additive in action for each nematode species independently.